Microelectronic imagers are well known to those having skill in the electronics/photonics art, as they are used in digital cameras, wireless devices with picture capabilities, and many other applications. Cellular telephones and Personal Digital Assistants (PDAs), for example, are incorporating microelectronic imagers for capturing and sending pictures. The growth rate of microelectronic imagers has been steadily increasing as they become smaller and produce better images with higher pixel counts.
Microelectronic imagers include image sensors that use Charged Coupled Device (CCD) systems, Complementary Metal-Oxide Semiconductor (CMOS) systems, or other solid state systems. CCD image sensors have been widely used in digital cameras and other applications. CMOS image sensors are quickly becoming very popular because they have low production costs, high yields, and small sizes, CMOS image sensors, as well as CCD image sensors, are accordingly “packaged” to protect the delicate components and to provide external electrical contacts. Optically interactive microelectronic devices require packaging that provides protection from other environmental conditions while allowing light or other forms of radiation to pass through to a surface where sensing circuitry is located. One problem with conventional packaging techniques of microelectronic devices is that the final packages produced allow for the exposure of the image sensor to amounts of unwanted peripheral light.
Furthermore, the materials and structures involved in conventional semiconductor packaging techniques require fabrication processes that can be time consuming and require several precision assembly steps. Each assembly step increases the opportunity for contamination or damage to the imaging device itself, raising defect levels and slowing production time to avoid such damage and contamination. Additionally, if the package design or fabrication approach necessitates that all of the imager die located on a wafer be packaged regardless of whether a significant number of die are defective, a substantial waste of material results. Due to the extremely cost-competitive nature of the semiconductor industry, improvements in product yield and production time are of value, especially when considered in terms of the high volume of components being manufactured.
There is a need for methods to both improve the quality, and decrease the cost, of an imaging device. Specifically, there is a need for providing a method that enables low-cost, high volume encapsulated packaging of imager die while providing a high quality imaging device.